1. Field of the Invention
The present invention relates to a medium supplying apparatus and an image forming apparatus.
2. Description of the Related Art
Conventional image forming apparatus such as printers, copying machines, and facsimile machines include a medium supplying apparatus that feeds sheets of paper to image forming sections.
A medium supplying device is generally of two types: a feed roller-and-friction separator type and a feed roller-and-retarding roller type. For the feed-roller-and-friction separator type, a stack of paper is placed on a paper-supporting platform and a feed roller feeds a top page of the stack of paper into a paper transport path. The medium supplying apparatus includes a separator having a friction creating material in contact with the feed roller. When two or more pages of paper are pulled in between the feed roller and the separator, the separator applies a drag so that only the top page of the stack of paper is fed into the paper transport path.
For the feed roller-and-retarding roller type, a medium feeding member is provided in pressure contact with a top page of a stack of paper raised to a certain level. The medium feeding member includes a pickup roller and a pair of rollers. The pickup roller advances the paper toward a paper transport path. The pair of rollers includes a feed roller and a retarding roller that serves to separate the paper page by page. The retarding roller applies a force that tends to advance the paper in the opposite direction to the feed roller. When only one page of the paper is fed to the retarding roller, the friction between the retarding roller and the paper causes the paper to advance the paper in the forward direction. When more than one page of the paper is advanced, the retarding roller applies a braking force to the paper to separate the pages of the paper so that only the top page is advanced.
The medium supplying apparatus of a feed roller-and-retarding roller type also requires an up-down mechanism that controls the height of a plate-like support on which a stack of paper is held and a medium guide that limits the width of the paper. Therefore, the medium supplying apparatus is necessarily of large overall size.
For accommodating long paper such as A3 paper, for example, a Multi Purpose Tray (MPT) or a manual supply tray may be employed. However, installing the MPT or the manual feeding tray requires a large space and therefore the overall size of the medium supplying apparatus becomes even larger.